Antimicrobial Activity of Nickel Nanoparticles Against Clinically Relevant Bacterial Pathogens

The increasing prevalence of antimicrobial-resistant bacterial pathogens has created an urgent need for alternative antimicrobial strategies. Nanotechnology has attracted considerable attention because nanoparticles possess physicochemical properties that allow them to interact with microorganisms through several mechanisms simultaneously. Among metallic nanomaterials, nickel nanoparticles (NiNPs) and nickel oxide nanoparticles (NiO-NPs) have demonstrated promising antibacterial activity against both Gram-positive and Gram-negative bacteria. This literature-based research article evaluates the antimicrobial activity of nickel nanoparticles against clinically relevant bacterial pathogens, with emphasis on Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterococcus faecalis, and other opportunistic pathogens. Published studies were reviewed with attention to nanoparticle synthesis, physicochemical characteristics, antibacterial testing methods, observed inhibition, and proposed mechanisms of action. The reviewed evidence indicates that antibacterial activity is influenced by nanoparticle size, morphology, surface characteristics, concentration, synthesis method, bacterial species, and experimental conditions. Nickel-based nanoparticles have been associated with inhibition of bacterial growth, membrane disruption, oxidative stress, intracellular damage, and biofilm inhibition. Several studies also indicate stronger activity against particular Gram-positive organisms, although this pattern is not universal. Despite these promising findings, concerns regarding nickel-associated toxicity, nanoparticle aggregation, environmental persistence, and the limited number of standardized in vivo studies remain important barriers to clinical translation. Overall, nickel nanoparticles represent a potentially useful antimicrobial platform, but further standardized investigations are required before therapeutic applications can be established.